XenForo developer

There is a small amount that I could potentially look to do (without trying much more extensive changes), but it would likely only change IE (or Edge). Firefox seems to maintain the spaces without issue and the default paste handler in Chrome actually puts the paste onto a new line. With the paste handler, Edge has a trailing space (no leading space) which does get trimmed out.

More extensive changes would involve how we access pasted content, which isn't that trivial so it isn't something we would be changing at this point.

As such, I think this has to be a design issue (with a potential browser issue, since I don't know if Chrome even keeps those spaces).